Electrically tuned microwave energy device

ABSTRACT

A microwave energy device having cavity resonator means is electrically tuneable by means coupled to the resonator means including a short-circuited waveguide transmission line adapted to convert linearly polarized wave energy to circularly polarized wave energy and to receive and propagate such circularly polarized waves. A ferromagnetic material element is magnetized at a value below the saturation magnetization value (4 pi Ms) of the material. An electrical field coil provides a variable phase shift of the circularly polarized wave energy traversing the unsaturated element in one direction and, upon reflection by the short circuit, in a second direction. The phase shift of the circularly polarized waves traversing the partially magnetized unsaturated ferromagnetic material yields a tuning system for microwave generators of linearly polarized energy with an element of relatively short overall length.

United States Patent [191 Osepchuk et al.

[ May 6,1975

1 ELECTRICALLY TUNED MICROWAVE ENERGY DEVICE [75] Inventors: John M. Osepchuk, Concord;

Theodore Kohane, Sudbury, both of Mass.

[73] Assignee: Raytheon Company, Lexington,

Mass.

[22] Filed: Feb. 27, 1974 1 1 Appl. No.: 446,446

[52] US. Cl. 315/3955; 315/3959, 315/3977; 331/5; 333/21 A; 333/24 [51] Int. Cl. l-10lj 25/50 [58] Field of Search 315/3955, 39.57, 39.59,

[56] References Cited UNITED STATES PATENTS 2,752,495 6/1956 Kroger 315/3955 X 2,881,398 4/1959 Jones 333/24 R 3,139,592 6/1964 Sisson 331/5 3,178,652 4/1965 Scharfman et al... 331/5 3,333,148 7/1967 Buck 315/3977 X 3,334,267 8/1967 Plumridge 315/3955 3,714,592 1/1973 Jory 315/3951 3,760,300 9/1973 Leahy 333/21 R Primary Examiner-Saxfield Chatmon, Jr. Attorney, Agent, or FirmEdgar O. Rost; Joseph D.

Pannone; Harold A. Murphy ABSTRACT A microwave energy device having cavity resonator means is electrically tuneable by means coupled to the resonator means including a short-circuited waveguide transmission line adapted to convert linearly polarized wave energy to circularly polarized wave energy and to receive and propagate such circularly polarized waves. A ferromagnetic material element is magnetized at a value below the saturation magnetization value (4'rrMs) of the material. An electrical field coil provides a variable phase shift of the circularly polarized wave energy traversing the unsaturated element in one direction and, upon reflection by the short circuit, in a second direction. The phase shift of the circularly polarized waves traversing the partially magnetized unsaturated ferromagnetic material yields a tuning system for microwave generators of linearly polarized energy with an element of relatively short overall length.

7 Claims, 8 Drawing Figures PATENTEEHAY 6W5 3.882.352

sum 10F 4 CURRENT SOURCE TT MODE CAVITY 82 3 PHASE Al R W M v SHIFTER 7 C L 75 R 801 R2 ELEMENT MAGNETRON OUTPUT I LOAD RL I 2 SHORT l I PHASE SHIFTER ELEMENT PATENTEBHAY 6:925

SHEEI 2 BF 4 ELECTRICALLY TUNED MICROWAVE ENERGY DEVICE BACKGROUND OF THE INVENTION 1. Field of the Invention The invention relates to microwave energy devices and, in particular, electrical tuning utilizing ferromagnetic materials.

2. Description of the Prior Art Electrical tuning of microwave energy devices, such as coaxial magnetrons, utilizing ferromagnetic materials has been disclosed in U.S. Pat. No. 3,333,148 issued July 25, 1967 to D. C. Buck. In this embodiment a ferromagnetic material ring is disposed on one of the inner walls of cavity resonator means. An annular electromagnetic member is positioned outside of the cavity resonator and provides for biasing the material at its saturation magnetization value. By varying the electrical field the effective permeability of the ferromagnetic material is varied to thereby alter the resonance of the tuned circuit or cavity resonator.

Utilizing conventional ferromagnetic tuning techniques based on the variation of the permeability (pf) (real part) and dielectric constant (K of a saturated material with applied fields near the resonance value, resultshave indicated that tuning of less than 1 percent is generally available. Such a narrow tuning range requires a bias field of several thousand gauss, as well as -a driving field in the order of an additional thousand gauss. The closeness to resonance limits the tuning in view of the fact that excessive p." (imaginary part) close to resonance lowers the unloaded Q of the microwave energy source below acceptable values.

Still anotherprior art electrical tuning structure utilizing ferromagnetic materials is found in U.S. Pat. No. 3,334,267. issued Aug. 1, 1967 to R. F. Plumridge and assigned to the assignee of the present invention. In this embodiment a stabilizing cavity resonator is longitudinally displaced from the anode-cathode interaction circuit. A second cavity resonator is mutually inductively coupled to the stabilizing cavity resonatorand ferromagnetic materials are disposed in the mutually inductive regionbetween the respective cavity resonators. An external DC magnetic field is operatively associated with the ferromagnetic material to variably alter the effective permeability and thereby alter the mutual inductance between the cavity resonators with a corresponding variation in the resonant frequency of the microwave oscillations. The placement of the ferromagnetic materials in the mutually inductive region between first and second cavity resonators results in changes in the effective permeability tensor with a relatively smaller volume of material in comparison to prior art cavity resonator techniques having the ferromagnetic material directly loaded within the confines of the cavity. The reduction in the required ferromagnetic material volume also simplifies the externalmagnetic circuitry required. The mutually inductively coupled two-cavity resonator system also requires the operation of the ferromagnetic materials in the region above the saturation magnetization value with its attendant reduction of the unloaded Qs of the cavity resonators and the limited tuning range.

Another method of tuning is referred to as double- 576-582 inclusive. In accordance with the teachings of this system the magnetron is provided with two output terminals. The first terminal provides the power output coupling means while the second terminal is used to couple into the resonant system a reactance that changes the resonant frequency. The variable reactance is provided by a short-circuited transmission line having a variable length determined by movement of a chokeshorting plunger within a coaxial waveguide line. With this mechanical tuning arrangement it is' possible to have the actual tuning motion occur outside of the vacuum envelope of the tube by reason of a glass-tometal seal. This very feature, however, is a self-limitin g one in that the double-output tuning arrangement may be utilized in tuning microwave energy generators of only the low pulse-power output type in view of the fact that breakdown could occur in the tuner coaxial line or across the tuner vacuum seal at higher output powers. The nature of the tuner vacuum seal also limits the average output power of the microwave energy generator because the high radio frequency fields that generally exist in the glass for at least a portion of the tuning range may heat the glass to its melting point. Pulse powers of up to 10 kilowatts and average powers of up to 200 watts have, therefore, been achieved utilizing the known glass materials for the vacuum seal. Another limitation in this method of tuning is the circuit efficiency which becomes appreciably lowered from that of an untuned device. The method, however, has made possible tuning ranges of 10-20 percent at the lower output powers and has also provided a teaching of means of coupling electrically controlled reactances into a microwave energy generator which can be useful in methods of frequency modulation.

Tuning of microwave energy devices, particularly, coupled circuit electrical tuning methods can become more widely acceptable if the coupling coefficient of the tuning means is greater than the coupling coeffioutput tuning described in the text Microwave Mag- 'netrons, G. B. Collins, Vol. 6, Radiation Laboratory Series, McGraw-l-lill Book Company, Inc., 1948, pps.

cient of the power output structure to thereby minimize the overall insertion loss of the tuning means and the accompanying reduction of circuit efficiency. It may also be noted that, heretofore, the auxiliary tuning cavity resonator means with ferromagnetic materials disposed therein or in the coaxial cavity resonators involved, solely, the perturbation of linearly polarized waves. In view of the low cost, as well as reliability of the solid state materials and simplified circuitry, it is desirable to provide an improved system of electrical tuning which will obviate all the disadvantages of prior art known electrical and mechanical tuning systems.

SUMMARY OF THE INVENTION In accordance with the teachings of the invention a microwave energy device, for example, a magnetron is provided with tuning means coupled to the anodecathode interaction circuit utilizing circularly polarized wave energy converted from the typical linear polarization of energy in such devices. In one embodiment a short-circuited section of circular waveguide is closely coupled by means of an iris in an outer wall of a coaxial cavity resonator. Within the circular waveguide a longitudinally disposed and longitudinally magnetized ferromagnetic material element provides for a tuning rate based on Faraday rotation phase shift principles. The ferromagnetic material in accordance with the invention, however, is partially magnetized at a value below the saturation magnetization and resonance value or with saturated ferromagnetic materials. The magnetic field variation also requires substantially lessdriving.

power. Both reciprocal and nonreciprocal embodi-i ments of the invention are disclosed.

The tuning means provided in accordance with the v invention introduces a series resonant circuit closely coupled to the cavity resonator system of the microwave energy device. The phase shift characteristics are based on the effects of the ferromagnetic material upon negative circularly polarized waves which differ from the effects experienced by the positive circularly polarized waves. With the axial DC magnetic field parallel to the direction of propagation the respective circularly polarized components rotate and the phase shift 4) can" be expressed by the equation (b [(B- /3+)L]/2 In this equation 3+ is equal to the phase constant of the circularly polarized wave rotating in the same sense as the current. [3- is equal to the phase constant of the circularly polarized wave rotating in the opposite sense of 3+. L is the length of the ferromagnetic material element. The net rotation of the circularly polarized waves determines the net differential phase shift.

The behavior of ferromagnetic bodies when magnetized and disposed in the path of electromagnetic enthe sense of the input circular polarization between right hand and left hand-has the same effect upon the.

phase-current characteristics as reversing the currents of the tightly wound coils around circular waveguide which provides the longitudinal or axial magnetic biasing field. I

One embodiment of the invention is described utilizing TE modes and the teachings of the invention are equally applicable to the TE and TE modes. While a specific embodiment of the invention is described illustrating the utilization of'ferromagnetic rod elements the desired tuning may be attained through the utilization of spheres as well. The utilization of the unsaturatedferromagnetic material elements results in the provision of efficient tuning means for use in microwave energy-device s, particularly of the coaxial magnetron-type, with only one'wavelength of the material, as

well as, a moderate power driving field. Thermal prob lems involved in the"use.;.ofthe ferromagnetic. materials have also been effectively alleviated through the utilization of only partially magnetized materials below saturation magnetization to attain the desired phase shift 7 "characteristics. The term "fsaturatio'n magnetization is ergy has been described in the article The Elements of Ferrite Microwave Devices by C. Lester Hogan,

Proceedings of the I.R.E., Oct., 1956, pp. 1345-1368.

In the present specification the term circularly polarr' ized" is considered to be the electric fields of such waves which can be resolved vectorially into two orthogonal components of equal amplitude 90 apart in space and 90 apart in time. Additionally, the term right hand circular polarization" is defined as an electromagnetic wave which is propagated in a manner similar to that of a right hand screw so that when travelling away from the observer its observed direction of rotation is clockwise. The term left hand circular polarization is considered as being in the opposite direction of rotation or counterclockwise. In Faraday phase shifters it is known that the rotation of a planar polarization as well as the phase shift of the waves transmitted through the ferromagnetic material are functions of left and right hand circularly polarized phase constants. Additional details may be obtained in the article by Sakiotis and Chait, entitled Ferrites at Microwaves", Proceedings of the I.R.E., Vol. 41, pp. 8793, Jan. 15, 1953;

With a positive coil current and right hand circular polarization the phase of the waves is advanced while negative currents result in a phase delay. The term phase delay" denotes that the effective electrical length of the overall phase shifter means becomes longer due to the changes in the microwave permeability of the ferromagnetic material. Conversely, left hand circular polarization input results in an output which is delayed in phase for positive currents and advanced in phase for negative currents. It may also be noted that reversing defined as the value of magnetization corresponding to complete alignment of all the magnetic spins at 0K. While the invention is'described'as operating in the analoguefashion it'is also possible to provide a structure operating in the digital modeemploying ferromagnetic latching techniques.

BR-IEF'DESCRIPTION or THE DRAWINGS Details of illustrative}embodiments of the invention will be described with reference being directed to the accompanying drawings,fwhe rein:-

FIG. 1 is a perspective embodying the invention;

5 FIG. 2' is a diagrammatic representation of an embodiment of the invention for reciprocal operation;

. FIG. 3 is a diagrammatic representation of a nonreciprocal embodiment of the invention;

FIG. 4 is a schematic'circuit diagram 'lentcircuit of the externally embodying the invention;

FIG. 5 is adetailed cross-sectional view of a coaxial magnetron; I

FIG. 6 is a detailed cross-sectional view of the external tuning structure embodying the invention which is coupledto the magnetron illustrated in FIG. 5;

FIG. -7 is a graph illustrative of the phase-current characteristics of a ferromagnetic phase shifter propagating circularly polarized wave energy; and

FIG. 8 is a detailed cross-sectional view of an alterna-' tive microwave device of the internal coaxial cavity resonator type together with the tuning structure of the invention.

DESCRIPTION OF A PREFERRED EMBODIMENT FIG. 1 illustrates the embodiment of the invention 10 of the coaxial magnetron type including a metallic enposition diametrically opposite to the output coupler 14. The details of the microwave magnetron will now be described with reference being directed to FIGS.

The microwave device 10 comprises a metallic envelope 12 defined by end' cover members 18 and 20 herview of a coaxial magnetron of the equivatuned coaxial magnetron metically sealed to a cylindrical wall member 22 to pro- 'vide a vacuum tight enclosure. Anode vanes 24 supported by the common boundary wall 26 define cavity resonators therebetween circumferentially disposed about the central cathode emitter 28 with an intervening interaction region to comprise the well-known anode-cathode resonant circuit in such devices. The cathode 28 is supported by an assembly 30 including outer tubular member 32 secured to magnetic pole piece 34. All the electrical leads for energizing the cathode structure and to provide the electric field potentials to operate the device extend within the cathode assembly 30. Conventional tubes of the type under consideration typically operate in the pimode of oscillation over the tunable frequency range which is controlled by an outer coaxial cavity resonator 36 operating in, illustratively, the TE mode.

The outer coaxial cavity resonator 36 is defined by cylindrical outer wall member 22 and the common boundary wall 26 together with the end covers 18 and 20. The energy generated in the anode-cathode resonant circuit is coupled to the outer coaxial cavity resonator 36 by means of spaced longitudinal slots 38 operatively associated with the anode cavity resonators. Extraneous modes may be suppressed by lossy rings 40 and 42 of such materials as carbonized alumina ceramic, barium titanate or ferrite to provide a high di electric loss.

The magnetic fields within the anode-cathode resonant circuit, as well as, the outer coaxial cavity resonator 36 are provided by means including oppositely disposed pole piece members 34 and 44 with the magnetic field extending parallel to the axis of the cathode 28. The electric field lines extend perpendicular to the magnetic fields and thereby provide for the crossed field type of electron interaction in this class of microwave devices. Two external C-shaped permanent magnets contact the pole piece members and have not been illustrated in the interest of simplifying the description.

The microwave frequency energy generated bythe I crossed field magnetron is coupled from the outer coaxial cavity resonator 36 through an iris 46 and a transformer section 48 which may, for example, be H- shaped. A dielectric window 50 supported within a flange assembly 52 hermetically seals the envelope and permits the passage of the microwave energy to be coupled to a utilization load which may be coupled to a rectangular output flange 54. In prior art devices a tuner assembly including an axially translated tuning ring member positioned within the external cavity reso-' nator 36 would be mechanically actuated by gearing arrangements housed within a tubular member such as member 57 adjacent to magnetic pole piece member 44.

An electrical tuning system 16 incorporating ferromagnetic phase-shifting means in accordance with the teachings of the invention is coupled to wall member 22 by means of a resonant iris 56 and will be described with reference now being directed to FIGS. 2 and 3. FIG. 2 is illustrative'of reciprocal type operation and comprises a section of circular waveguide 58 which is short-circuited at the outer end 60. A nonreciprocal Faraday rotator section 62 includes a first ferromagnetic element 64 such as a one-wavelength long rod 64 of a ferromagnetic material, such as yttrium iron garnet or any of the other well-known ferrite materials utilized for phase shifters. A longitudinal magnetic field extending parallel to the direction of propagation of the energy is provided by magnetic field producing means 66 illustrated as of the permanent magnet type. A quarterwave circular polarizer plate 68 of a dielectric material is diametrically disposed within the circular waveguide 58. Typically such plate members are oriented at an angle of 45 to provide for the conversion and propagation of linearly polarized waves emanating from the outer coaxial cavity resonator 36 and Faraday rotator 62 to circularly polarized waves which then traverse the unsaturated ferromagnetic phase shifter section 70.

The circularly polarized wave energy traverses a second ferromagnetic element 72 having a partially magnetized longitudinal field provided by means of a field coil 74 tightly wound around. the circular waveguide 58. The magnetization of the ferromagnetic element is controlled to be below the saturation magnetization value of the material. Variations in coil current with DC and/or AC produce a predetermined net phase shift in a first direction and upon reflection from the short circuit means 60, in an opposite direction for a second traversal. The shifted circular waves are reconverted to linearly polarized energy by circular polarizer 68 and again experience a Faraday rotation before being reintroduced into the outer coaxial cavity resonator system to vary the resonant frequency of the magnetron.

Rapid electrical tuning at rates analogous to dither tuning can be achieved with circularly polarized wave energy traversing unsaturated ferromagnetic phaseshifting means in a coupled circuit arrangement. With unsaturated ferromagnetic material (411M 4-n'Ms) large variations of the permeability tensor components K and p. are utilized to obtain a relatively large phase shift value with an element length of, typically, only one wavelength of the operating frequency. in comparison to prior art saturated type phase shifters which require elements five wavelengths long. The disclosed electrical tuning system provides for tuning of the mi crowave magnetron in a manner somewhat analogous to the double-output tuning method. The equivalent circuit of the present system which operates as aseries resonant circuit is illustrated in FIG. 4. The. normal 10- cation of the iris 56 in the outer wall member 22 of the magnetron 10 is a low impedance point of the magnetron cavity resonator to minimize insertion loss introduced by the tuning structure. The magnetron pi-mode cavity components are represented by the capacitance 76, inductance 78 and resistance 80 and are coupled to the magnetron output load R, The equivalent circuit loss of a short-circuited section of circular guide having an overall length L, an impedance Z; and phase constant B is indicated as a resistance 82 and designated R Utilizing the coupled circuit tuning equations, particularly on pages 579 and 580 of the Collins reference, it may be noted that electrical tuning with the system of the present invention results in a circuit efficiency We QEt/Qu! QE1/QE2(R2/Z2)] (2) Extrapolation of data, as well as theoretical consideration, leads to the conclusion that for typical coaxial magnetron operation tuning ranges of 1.5 to 3 percent may be realized with little degradation of the unloaded Q or circuit efficiency. Even wider tuning ranges may be achieved utilizing ferromagnetic elements other than the rods such as, for example, a sphere on axis with the coupling of magnetodynamic modes in the tuning system.

FIG. 3 illustrates a nonreciprocal embodiment wherein the circular polarizer and Faraday rotator are combined in a unitary element of a ferromagnetic material 84. A plurality of small magnets 86 are disposed in close proximity to guide 58 to provide the element 84 with a quadrupolar DC magnetic field. Second element 88 is the unsaturated ferromagnetic phaseshifting means and tightly wound field coil 90 provides the driving field for the predetermined phase shift variations. Either the tuning system shown in FIG. 2 or the one in FIG. 3 may be utilized dependent on availability of ferromagnetic materials, as well as space or other considerations.

Referring to FIG. 6 the coupled-circuit electrical tuning system 16 of the invention appended to outer cavity resonator 36 by attachment to wall 22 will now be described. Linearly polarized wave energy is introduced into a section of circular waveguide 92 by means of a resonant iris 56 in wall 22 (shown in FIG. A first section comprises a Faraday rotator having ferromagnetic element 94 and magnetic field producing means 96, such as a permanent magnet. The rotator typically provides a predetermined angle of rotation, illustratively 45, in the forward as well as reverse directions although the angular displacement is nonreciprocal. Linearly polarized waves represented by arrow 98 entering the Faraday section are launched after traversal in a first direction as a wave indicated by arrow 100. Ferromagnetic element 94 is supported within the circular waveguide by any suitable low loss dielectric means 102. The input energy is next converted into circularly polarized wave energy represented by vector 104 by means of circular polarizer 106 comprising a diametrically positioned quarter-wave dielectric plate. The cicular polarizer 106 is supported within a metallic frame member 108.

The next section comprises the phase-shifting means including the unsaturated ferromagnetic element 110 supported within by dielectric means 112. The means for partially magnetizing ferromagnetic element 110 and producing the phase shift variations includes single field coil 114. A longitudinal magnetic field bias extends parallel to the direction of the propagation of the energy. The ferromagnetic element is partially magnetized and remains below the magnetization saturation value. Leads 116 provide for the connection of the field coil 114 to the external circuitry. The overall structure is terminated by waveguide short-circuit means 118 to thereby reflect substantially all of the circularly polarized wave energy in a direction opposite to a first direction through the ferromagnetic element to thereby provide a combined predetermined phase shift characteristic of the energy. In FIG. 6 circular arrow 104 has been indicated as being phase shifted a predetermined number of degrees indicated by the symbol 4: Upon reflection from the short-circuit means 118 the reflected circularly polarized wave energy encounters a second phase shift which has been indicated by the symbol Referring next to FIG. 7 a description of the operation of the ferromagnetic phase-shifting means will be briefly explained as presently understood. The coordinates of the graph are phase shift it along the vertical coordinate and current I with the polarities indicated by the and symbols. Curve 120 represents th phase-current characteristics of right hand circularly.

' (RI-IP) polarized wave energy. For negative current values a phase delay is provided while for positive currents there is a phase advance. Curve 122 represents the same characteristics for circularly polarized wave energy of the opposite sense or left hand (LHP) with a phase advance for negative currents and a phase delay for positive currents. If we assume that the ferromagnetic element is magnetized below saturation this is indicated by the dashed line 124 and current value I If the circular wave 104 in FIG. 6 is assumed to be right hand circularly polarized and the magnetic current H is maintained, the wave energy in the first transversal encounters a phase advance indicated by (b as indicated by the dashed line 126. After reflection and a second transversal through the ferromagnetic element, a phase delay of (b as indicated by the dashed line 128, is experienced. Short-circuit means 118 provide a reflected wave which will have the same sense of circular orientation and, upon recombining vectorially, the reflected components become a mirror image of the original incident wave. In view of the fact that a phase advance is simply a negative phase delay, the two phase shifts are added to obtain a net differential phase shift (15 4J which is equivalent to (b as indicated by the dashed line 130. The phase-shifting means are completely reciprocal so that the input right hand or left hand circularly polarized wave energy will encounter the same net phase shift. Hence, if left hand waves are received at the input and the same current I, is maintained, the phase delay and phase advance would again be added to result in a net phase shift If the electrical current is reversed then again a net phase shift would be produced as indicated on the I side of the graph.

Upon egress of circularly polarized wave 104 having the net phase shift rb the circular polarizer 106 converts this energy into linearly polarized wave energy which then enters the Faradayrotator section as indicated by the arrow 132. After traversing the Faraday rotator element 94 the linear wave vector is again angularly displaced as indicated by the arrow 134 for passage to the cavity resonator with the desired phase shift to result in tuning of the magnetron resonant frequency. The Faraday rotator, circular polarizer and phase-shifting means are supported within an outer cylindrical member 136 which may be fabricated in two parts having an intermediate electrical isolation means, such as a ceramic spacer 138, as illustrated in FIG. 6.

Referring next to FIG. 8 an alternative embodiment of the invention comprising an internal coaxial cavity resonator magnetron 140 is illustrated. In this embodiment the anode cylinder 142 provides an internal axial cavity 144 having one end sealed off by means of microwave permeable window 146 and the energy is cou- The anode-cathode resonant circuit is provided concentrically outside of the cavity resonator 144 and includes a plurality of radially disposed vane elements 154 with the energy being coupled to the internal cav-. I ity resonator by means of slots 156 in the anode cylinder wall 142. A cathode emitter ring 158 is coaxially disposed around the anode cylinder and is supported by an electrical insulator member 160.

The magnetic field producing means for the anodecathode resonant circuit is provided by means of magnetic pole pieces 162 and 164 supported by concentric discs 166 and I68 at one end and the cathode insulator 160 at the other end. External C-shaped magnets (not shown) positioned adjacent to the outer ends of the pole piece members direct the magnetic field parallel to the axis of the cathode.

The electrical tuning system of the invention is provided within the section of circular waveguide 170 with the linearly polarized energy being coupled through the window and iris arrangement 152. The tuning structure illustrated is similar to FIG. 2, however, the nonreciprocal arrangement shown in FIG. 3 may also be incorporated. In the reciprocal arrangement a first section comprises a Faraday rotator ferromagnetic element 172 together with a biasing permanent magnet 174. The circular polarizer comprises quarter-wave dielectric plate 176 and the circularly polarized wave energy is phase shifted by ferromagnetic element 178 operatively associated with the field coil 180. The energy reflection means comprises waveguide shorting means 182 enclosing the end of the circular waveguide 170. The generated linearly polarized energy from the internal cavity resonator 144 is again first rotated a predetermined number of degrees by the Faraday rotator and then the energy is circularly polarized. The circularly polarized energy experiences a predetermined phase shift in a first direction and then in a reverse direction upon reflection of substantially all of the energy from the short-circuit means. The energy is again returned to the cavity resonator means in the proper vectorial orientation with the desired tuning achieved by the electrical phase shift variations. The output energy is coupled through the coupling arrangement 150 axially disposed with respect to the tuning means. Again as in the prior embodiments, the tuning is controlled solely by the electrical coil means operatively associated with an unsaturated ferromagnetic material and rapid tuning rates over moderate tuning ranges may be achieved.

Numerous variations, modifications and alterations will be evident to those skilled in the art. It is intended, therefore. that the foregoing description of illustrative embodiments of the invention be considered in the broadest aspects and not in a limiting sense.

We claim:

1. A microwave energy device comprising:

means for generating electromagnetic energy at a predetermined frequency including cavity resonator means;

coupled-circuit means for electrically tuning said device including a transmission line electrically coupled with said cavity resonator means;

said transmission line having mounted therein, in the order named, a circular polarizer for converting linear to circularly polarized wave energy. ferromagnetic phase-shifting means, short circuit means enclosing an end to reflect substantially all of the circularly polarized energy incident thereon;

magnetic field producing means including a source of electric current positioned in the region of said phase-shifting means to provide said ferromagnetic material with an internal magnetization field below the saturation magnetization value of said material and produce a variable phase shift of circularly polarized wave energy propagated therethrough in forward and reverse directions;

output energy coupling means electrically coupled to said cavity resonator means at a location separate and apart from said coupled-circuit means.

2. The device according to claim 1 wherein said coupled-circuit means further include ferromagnetic Faraday rotator means for angular displacement of linearly oriented energy positioned in proximity to the end of said transmission line coupled to said cavity resonator means.

3. The device according to claim 2 wherein said Faraday rotator means and circular polarizer comprise a single ferromagnetic material element.

4. The device according to claim 1 wherein said ferromagnetic phase-shifting means comprise an element of approximately one wavelength of said frequency in length.

5. The device according to claim 1 wherein said circular polarizer comprises a diametrically disposed plate member of dielectric material one-quarter of a wavelength of said frequency in length.

6. The device according to claim 1 wherein said transmission line comprises a section of circular waveguide.

7. A crossed field microwave energy oscillator comprising:

an anode-cathode interaction resonant circuit system including a plurality of circumferentially disposed cavity resonators defined by anode elements;

coaxial cavity resonator means adapted to be resonant at a predetermined frequency; and

coupled-circuit means for electrically varying said frequency comprising a section of circular waveguide connected to said coaxial cavity resonator means;

a circular polarizer adapted to convert said energy to circularly polarized wave energy positioned within said waveguide;

a ferromagnetic element positioned along the longitudinal axis of said waveguide for producing a phase shift of said circularly polarized wave energy;

means for short-circuiting the end of said waveguide to substantially reflect all of said circularly polarized wave energy;

magnetic field producing means including an electric field coil positioned in the region of said ferromagnetic phase-shifting element to provide an unsaturated internal magnetization field parallel to the direction of propagation of said energy and variable phase-shift of circularly polarized wave energy propagated in said element in opposing directions; and

means for coupling said energy from said oscillator coupled to said cavity resonator means. 

1. A microwave energy device comprising: means for generating electromagnetic energy at a predetermined frequency including cavity resonator means; coupled-circuit means for electrically tuning said device including a transmission line electrically coupled with said cavity resonator means; said transmission line having mounted therein, in the order named, a circular polarizer for converting linear to circularly polarized wave energy, ferromagnetic phase-shifting means, short circuit means enclosing an end to reflect substantially all of the circularly polarized energy incident thereon; magnetic field producing means including a source of electric current positioned in the region of said phase-shifting means to provide said ferromagnetic material with an internal magnetization field below the saturation magnetization value of said material and produce a variable phase shift of circularly polarized wave energy propagated therethrough in forward and reverse directions; output energy coupling means electrically coupled to said cavity resonator means at a location separate and apart from said coupled-circuit means.
 2. The device according to claim 1 wherein said coupled-circuit means further include ferromagnetic Faraday rotator means for angular displacement of linearly oriented energy positioned in proximity to the end of said transmission line coupled to said cavity resonator means.
 3. The device according to claim 2 wherein said Faraday rotator means and circular polarizer comprise a single ferromagnetic material element.
 4. The device according to claim 1 wherein said ferromagnetic phase-shifting means comprise an element of approximately one wavelength of said frequency in length.
 5. The device according to claim 1 wherein said circular polarizer comprises a diametrically disposed plate member of dielectric material one-quarter of a wavelength of said frequency in length.
 6. The device according to claim 1 wherein said transmission line comprises a section of circular waveguide.
 7. A crossed field microwave energy oscillator comprising: an anode-cathode interaction resonant circuit system including a plurality of circumferentially disposed cavity resonators defined by anode elements; coaxial cavity resonator means adapted to be resonant at a predetermined frequency; and coupled-circuit means for electrically varying said frequency comprising a section of circular waveguide connected to said coaxial cavity resonator means; a circular polarizer adapted to convert said energy to circularly polarized wave energy positioned within said waveguide; a ferromagnetic element positioned along the longitudinal axis of said waveguide for producing a phase shift of said circularly polarized wave energy; means for short-circuiting the end of said waveguide to substantially reflect all of said circularly polarized wave energy; magnetic field producing means including an electric field coil positioned in the region of said ferromagnetic phase-shifting element to provide an unsaturated internal magnetization field parallel to the direction of propagation of said energy and variable phase-shift of circularly polarized wave energy propagated in said element in opposing directions; and means for coupling said energy from said oscillator coupled to said cavity resonator means. 